Mobile terminal

ABSTRACT

Provided is a mobile terminal switchable from a first state to a second state extended in a first direction, the mobile terminal comprising: a first frame; a second frame slidable in the first direction or in a second direction opposite to the first direction, with respect to the first frame; a roller coupled to the end of the second frame in the first direction; a flexible display part including a fixing part coupled to the first frame and a variable part which has a variable area, extends from the fixing part in a direction toward the rear surface thereof while surrounding the roller, and is positioned on the front surface according to the sliding movement of the second frame; and a rolling hinge positioned on the rear surface of the variable part and changing correspondingly to the shape of the variable part, wherein the roller includes a sawtooth part formed on the outer surface thereof, and the rolling hinge includes a concave-convex part corresponding to the sawtooth part.

TECHNICAL FIELD

The present disclosure relates to a mobile terminal, and more particularly, to a mobile terminal that has a flexible display and is capable of extending a size of a screen while the display is scrolled and slid at the same time.

BACKGROUND

Terminals may be generally classified as mobile/portable terminals or stationary terminals according to their mobility. Mobile terminals may also be classified as handheld terminals or vehicle mounted terminals according to whether or not a user can directly carry the terminal.

A display device is a device having a function of receiving, processing, and displaying a video that a user may watch. For example, the display device receives a broadcast selected by the user from broadcast signals transmitted from a broadcasting station, separates a video signal from the received signals, and displays the separated video signal on a display.

In recent years, because of a development of a broadcasting technology and a network technology, functions of the display device have also been considerably diversified, and a performance of the device has been improved accordingly. That is, the display device has been developed to provide not only broadcast contents but also various other contents to the user. For example, the display device may provide game play, music listening, internet shopping, user customized information, and the like using various applications as well as programs received from the broadcasting station. In order to perform such extended functions, the display device may be basically connected to other devices or networks using various communication protocols, and may provide the user with a ubiquitous computing environment. In other words, the display device has evolved into a smart device that enables connectivity to a network and continuous computing.

Recently, a flexible display having sufficient elasticity and capable of large deformation has been developed. The size of a mobile terminal can be varied using the deformable nature of the flexible display. For the mobile terminal having such a variable structure, changing the size of the mobile terminal should be stably performed, and there is a need for a structure to support the extended display unit to maintain a flat state of the display unit.

SUMMARY Technical Problem

An object of the present disclosure is to provide a mobile terminal for improving the durability of a flexible display by preventing a point at which the flexible display is bent from being limited to a specific position.

Another object of the present disclosure is to improve the utility of a flexible display by preventing the flexible display from being wavy.

Technical Solutions

Provided is a mobile terminal capable of switching a state thereof from a first state to a second state extended in a first direction including a first frame, a second frame capable of sliding in a first direction or in a second direction opposite to the first direction relative to the first frame, a roller coupled to an end in the first direction of the second frame, a flexible display unit including a fixed portion coupled to the first frame and a variable portion extending in a rearward direction from the fixed portion while surrounding the roller and having an area located at the front variable based on the sliding movement of the second frame, and a rolling hinge located on a rear surface of the variable portion and changing based on a shape of the variable portion, wherein the roller includes teeth formed on an outer surface thereof, wherein the rolling hinge includes irregularities corresponding to the teeth.

The rolling hinge may include a plurality of support bars extending in a third direction perpendicular to the first direction and arranged adjacent to each other in the first direction, and the teeth of the roller may include each protrusion inserted between adjacent two of the plurality of support bars.

The roller may include a fixed shaft fixed to the second frame, a driving shaft rotating relative to the fixed shaft, a coil spring having one side coupled to the fixed shaft and the other side coupled to the driving shaft, and a rotating cylinder rotating together with the driving shaft and having the teeth formed thereon.

The rotating cylinder and the driving shaft may rotate when the second frame moves and change the number of turns of the coil spring, and the coil spring may provide elasticity to restore the reference number of turns to the driving shaft and the rotating cylinder.

The elasticity of the coil spring may be provided when restoring the first state from the second state.

The second frame may include a roller seating portion for accommodating the roller therein at the end in the first direction thereof, and the roller seating portion may include a fixing hole for receiving a screw fastened through one end of the fixed shaft, and a bearing for one end of the driving shaft to be rotatably seated.

At least a portion of the driving shaft may rotatably overlap the fixed shaft inside of the coil spring.

The fixed shaft may include a first coupling groove for receiving one end of the coil spring, and the driving shaft may include a second coupling groove for receiving the other end of the coil spring.

Both of the ends of the coil spring may be bent in a radial direction of the coil, and the first coupling groove and the second coupling groove may extend through a center of rotation of the driving shaft.

The first coupling groove and the second coupling groove may respectively extend to the other end of the fixed shaft and the other end of the driving shaft.

The roller may include a plurality of rollers spaced apart from each other in a third direction perpendicular to the first direction.

Advantageous Effects

The mobile terminal according to the present disclosure may adjust the size of a screen according to the need, thereby satisfying both portability and utility.

The mobile terminal according to the present disclosure may prevent the display from being damaged since stress is not concentrated at a specific point of the display.

The mobile terminal may prevent the display from being wavy when the second frame moves, that is, keep the flatness of the display when the second frame moves.

The mobile terminal includes a structure for guiding the frames to move in parallel, thereby achieving stable state transition. Further scope of applicability of the present disclosure will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a mobile terminal in accordance with the present disclosure;

FIG. 2 is a front view of a first state and a second state of the mobile terminal in accordance with an embodiment;

FIG. 3 is a rear view of the first state and the second state of the mobile terminal in accordance with an embodiment;

FIGS. 4 and 5 are exploded perspective views of the mobile terminal in accordance with an embodiment;

FIG. 6 is a side view of the mobile terminal as viewed from a third direction;

FIG. 7 is a view showing a driving unit of the mobile terminal in accordance with an embodiment;

FIG. 8 is a cross-sectional view taken along lines A-A and B-B in FIG. 2 ;

FIG. 9 is a view illustrating a display unit and a rolling plate of the mobile terminal in accordance with an embodiment;

FIG. 10 is a view illustrating an issue raised in an extendable mobile terminal;

FIG. 11 is a cross-sectional view taken along lines C-C and D-D in FIG. 2 ;

FIG. 12 is a cross-sectional view taken along lines E-E and F-F in FIG. 11 ;

FIG. 13 is a view showing an expanded side portion and a guide hook of the mobile terminal in accordance with an embodiment;

FIG. 14 is a view showing a rolling hinge of the mobile terminal with an embodiment ;

FIG. 15 is a graph showing phase distortion in the mobile terminal;

FIG. 16 is a conceptual view for explaining causes of the phase distortion of FIG. 15 ;.

FIG. 17 is a view showing coupling of a roller and a rolling hinge of a body of a mobile terminal;

FIG. 18 is an exploded perspective view of a roller of a mobile terminal;

FIG. 19 is a view showing an order of fastening each component of a roller;

FIG. 20 is a view showing a cross-section based on rotation of a roller; and

FIG. 21 is a view showing arrangement of rollers coupled to a second frame of the present disclosure.

DETAILED DESCRIPTION

Description will now be given in detail according to exemplary embodiments disclosed herein, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components may be provided with the same reference numbers, and description thereof will not be repeated. In general, a suffix such as “module” and “unit” may be used to refer to elements or components. Use of such a suffix herein is merely intended to facilitate description of the specification, and the suffix itself is not intended to give any special meaning or function. In the present disclosure, that which is well-known to one of ordinary skill in the relevant art has generally been omitted for the sake of brevity. The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings.

It will be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another.

It will be understood that when an element is referred to as being “connected with” another element, the element can be directly connected with the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly connected with” another element, there are no intervening elements present.

A singular representation may include a plural representation unless it represents a definitely different meaning from the context.

Terms such as “include” or “has” are used herein and should be understood that they are intended to indicate an existence of several components, functions or steps, disclosed in the specification, and it is also understood that greater or fewer components, functions, or steps may likewise be utilized.

FIG. 1 is a block diagram of a mobile terminal in accordance with the present disclosure.

The mobile terminal 100 is shown having components such as a wireless communication unit 110, an input unit 120, a sensing unit 140, an output unit 150, an interface unit 160, a memory 170, a controller 180, and a power supply unit 190. Referring now to FIG. 1 , the mobile terminal 100 is shown having wireless communication unit 110 configured with several commonly implemented components. It is understood that implementing all of the illustrated components is not a requirement, and that greater or fewer components may alternatively be implemented.

More specifically, the wireless communication unit 110 typically includes one or more modules which permit communications such as wireless communications between the mobile terminal 100 and a wireless communication system, communications between the mobile terminal 100 and another mobile terminal, communications between the mobile terminal 100 and an external server. Further, the wireless communication unit 110 typically includes one or more modules which connect the mobile terminal 100 to one or more networks.

To facilitate such communications, the wireless communication unit 110 includes one or more of a broadcast receiving module 111, a mobile communication module 112, a wireless Internet module 113, a short-range communication module 114, and a location information module 115.

Regarding the wireless communication unit 110, the broadcast receiving module 111 is typically configured to receive a broadcast signal and/or broadcast associated information from an external broadcast managing entity via a broadcast channel. The broadcast channel may include a satellite channel, a terrestrial channel, or both. In some embodiments, two or more broadcast receiving modules 111 may be utilized to facilitate simultaneously receiving of two or more broadcast channels, or to support switching among broadcast channels.

The mobile communication module 112 can transmit and/or receive wireless signals to and from one or more network entities. Typical examples of a network entity include a base station, an external mobile terminal, a server, and the like. Such network entities form part of a mobile communication network, which is constructed according to technical standards or communication methods for mobile communications (for example, Global System for Mobile Communication (GSM), Code Division Multi Access (CDMA), CDMA2000 (Code Division Multi Access 2000), EV-DO (Enhanced Voice-Data Optimized or Enhanced Voice-Data Only), Wideband CDMA (WCDMA), High Speed Downlink Packet access (HSDPA), HSUPA (High Speed Uplink Packet Access), Long Term Evolution (LTE), LTE-A (Long Term Evolution-Advanced), and the like).

Examples of wireless signals transmitted and/or received via the mobile communication module 112 include audio call signals, video (telephony) call signals, or various formats of data to support communication of text and multimedia messages.

The wireless Internet module 113 is configured to facilitate wireless Internet access. This module may be internally or externally coupled to the mobile terminal 100. The wireless Internet module 113 may transmit and/or receive wireless signals via communication networks according to wireless Internet technologies.

Examples of such wireless Internet access include Wireless LAN (WLAN), Wireless Fidelity (Wi-Fi), Wi-Fi Direct, Digital Living Network Alliance (DLNA), Wireless Broadband (WiBro), Worldwide Interoperability for Microwave Access (WiMAX), High Speed Downlink Packet Access (HSDPA), HSUPA(High Speed Uplink Packet Access), Long Term Evolution (LTE), LTE-A (Long Term Evolution-Advanced), and the like. The wireless Internet module 113 may transmit/receive data according to one or more of such wireless Internet technologies, and other Internet technologies as well.

In some embodiments, when the wireless Internet access is implemented according to, for example, WiBro, HSDPA,HSUPA, GSM, CDMA, WCDMA, LTE, LTE-A and the like, as part of a mobile communication network, the wireless Internet module 113 performs such wireless Internet access. As such, the Internet module 113 may cooperate with, or function as, the mobile communication module 112.

The short-range communication module 114 is configured to facilitate short-range communications. Suitable technologies for implementing such short-range communications include BLUETOOTHTM, Radio Frequency IDentification (RFID), Infrared Data Association (IrDA), Ultra-WideBand (UWB), ZigBee, Near Field Communication (NFC), Wireless-Fidelity (Wi-Fi), Wi-Fi Direct, Wireless USB(Wireless Universal Serial Bus), and the like. The short-range communication module 114 in general supports wireless communications between the mobile terminal 100 and a wireless communication system, communications between the mobile terminal 100 and another mobile terminal 100, or communications between the mobile terminal and a network where another mobile terminal 100 (or an external server) is located, via wireless area networks. One example of the wireless area networks is a wireless personal area networks.

The location information module 115 is generally configured to detect, calculate, derive or otherwise identify a position of the mobile terminal. As an example, the location information module 115 includes a Global Position System (GPS) module, a Wi-Fi module, or both. If desired, the location information module 115 may alternatively or additionally function with any of the other modules of the wireless communication unit 110 to obtain data related to the position of the mobile terminal. As one example, when the mobile terminal uses a GPS module, a position of the mobile terminal may be acquired using a signal sent from a GPS satellite. As another example, when the mobile terminal uses the Wi-Fi module, a position of the mobile terminal can be acquired based on information related to a wireless access point (AP) which transmits or receives a wireless signal to or from the Wi-Fi module.

The input unit 120 includes a camera 121 for obtaining images or video, a microphone 122, which is one type of audio input device for inputting an audio signal, and a user input unit 123 (for example, a touch key, a push key, a mechanical key, a soft key, and the like) for allowing a user to input information. Data (for example, audio, video, image, and the like) is obtained by the input unit 120 and may be analyzed and processed by controller 180 according to device parameters, user commands, and combinations thereof.

Such cameras 121 may process image frames of still pictures or video obtained by image sensors in a video or image capture mode. The processed image frames can be displayed on the display unit 151 or stored in memory 170. In some cases, the cameras 121 may be arranged in a matrix configuration to permit a plurality of images having various angles or focal points to be input to the mobile terminal 100. As another example, the cameras 121 may be located in a stereoscopic arrangement to acquire left and right images for implementing a stereoscopic image.

The microphone 122 is generally implemented to permit audio input to the mobile terminal 100. The audio input can be processed in various manners according to a function being executed in the mobile terminal 100. If desired, the microphone 122 may include assorted noise removing algorithms to remove unwanted noise generated in the course of receiving the external audio.

The user input unit 123 is a component that permits input by a user. Such user input may enable the controller 180 to control operation of the mobile terminal 100. The user input unit 123 may include one or more of a mechanical input element (for example, a key, a button located on a front and/or rear surface or a side surface of the mobile terminal 100, a dome switch, a jog wheel, a jog switch, and the like), or a touch-sensitive input, among others. As one example, the touch-sensitive input may be a virtual key or a soft key, which is displayed on a touch screen through software processing, or a touch key which is located on the mobile terminal at a location that is other than the touch screen. On the other hand, the virtual key or the visual key may be displayed on the touch screen in various shapes, for example, graphic, text, icon, video, or a combination thereof.

The sensing unit 140 is typically implemented using one or more sensors configured to sense internal information of the mobile terminal, the surrounding environment of the mobile terminal, user information, and the like. For example,, the sensing unit 140 may alternatively or additionally include other types of sensors or devices, such as a proximity sensor 141 and an illumination sensor 142, a touch sensor, an acceleration sensor, a magnetic sensor, a G-sensor, a gyroscope sensor, a motion sensor, an RGB sensor, an infrared (IR) sensor, a finger scan sensor, a ultrasonic sensor, an optical sensor (for example, camera 121), a microphone 122, a battery gauge, an environment sensor (for example, a barometer, a hygrometer, a thermometer, a radiation detection sensor, a thermal sensor, and a gas sensor, among others), and a chemical sensor (for example, an electronic nose, a health care sensor, a biometric sensor, and the like), to name a few. The mobile terminal 100 may be configured to utilize information obtained from sensing unit 140, and in particular, information obtained from one or more sensors of the sensing unit 140, and combinations thereof.

The output unit 150 is typically configured to output various types of information, such as audio, video, tactile output, and the like. The output unit 150 is shown having a display unit 151, an audio output module 152, a haptic module 153, and an optical output module 154. The display unit 151 may have an inter-layered structure or an integrated structure with a touch sensor in order to facilitate a touch screen. The touch screen may provide an output interface between the mobile terminal 100 and a user, as well as function as the user input unit 123 which provides an input interface between the mobile terminal 100 and the user.

The audio output module 152 is generally configured to output audio data. Such audio data may be obtained from any of a number of different sources, such that the audio data may be received from the wireless communication unit 110 or may have been stored in the memory 170. The audio data may be output during modes such as a signal reception mode, a call mode, a record mode, a voice recognition mode, a broadcast reception mode, and the like. The audio output module 152 can provide audible output related to a particular function (e.g., a call signal reception sound, a message reception sound, etc.) performed by the mobile terminal 100. The audio output module 152 may also be implemented as a receiver, a speaker, a buzzer, or the like.

A haptic module 153 can be configured to generate various tactile effects that a user feels, perceive, or otherwise experience. A typical example of a tactile effect generated by the haptic module 153 is vibration. The strength, pattern and the like of the vibration generated by the haptic module 153 can be controlled by user selection or setting by the controller. For example, the haptic module 153 may output different vibrations in a combining manner or a sequential manner.

An optical output module 154 can output a signal for indicating an event generation using light of a light source. Examples of events generated in the mobile terminal 100 may include message reception, call signal reception, a missed call, an alarm, a schedule notice, an email reception, information reception through an application, and the like.

The interface unit 160 serves as an interface with various types of external devices that can be coupled to the mobile terminal 100. The interface unit 160, for example, may include any of wired or wireless ports, external power supply ports, wired or wireless data ports, memory card ports, ports for connecting a device having an identification module, audio input/output (I/O) ports, video I/O ports, earphone ports, and the like. In some cases, the mobile terminal 100 may perform assorted control functions associated with a connected external device, in response to the external device being connected to the interface unit 160.

The memory 170 is typically implemented to store data to support various functions or features of the mobile terminal 100. For instance, the memory 170 may be configured to store application programs executed in the mobile terminal 100, data or instructions for operations of the mobile terminal 100, and the like. Some of these application programs may be downloaded from an external server via wireless communication. Other application programs may be installed within the mobile terminal 100 at time of manufacturing or shipping, which is typically the case for basic functions of the mobile terminal 100 (for example, receiving a call, placing a call, receiving a message, sending a message, and the like). It is common for application programs to be stored in the memory 170, installed in the mobile terminal 100, and executed by the controller 180 to perform an operation (or function) for the mobile terminal 100.

The controller 180 typically functions to control overall operation of the mobile terminal 100, in addition to the operations associated with the application programs. The controller 180 may provide or process information or functions appropriate for a user by processing signals, data, information and the like, which are input or output, or activating application programs stored in the memory 170.

To drive the application programs stored in the memory 170, the controller 180 may be implemented to control a predetermined number of the components mentioned above with reference to FIG. 1 . Moreover, the controller 180 may be implemented to combinedly operate two or more of the components provided in the mobile terminal 100 to drive the application programs.

The power supply unit 190 can be configured to receive external power or provide internal power in order to supply appropriate power required for operating elements and components included in the mobile terminal 100. The power supply unit 190 may include a battery, and the battery may be configured to be embedded in the terminal body, or configured to be detachable from the terminal body.

Some or more of the components may be operated cooperatively to embody an operation, control or a control method of the mobile terminal in accordance with embodiments of the present disclosure. Also, the operation, control or control method of the mobile terminal may be realized on the mobile terminal by driving of one or more application problems stored in the memory 170.

FIG. 2 is a front view of a first state and a second state of the mobile terminal in accordance with an embodiment, and FIG. 3 is a rear view of the first state and the second state of the mobile terminal in accordance with an embodiment. FIGS. 2(a) and 3(a) are views showing the first state in which the mobile terminal is contracted, and FIGS. 2(b) and 3(b) are views showing the second state in which the mobile terminal is extended.

As shown in the figures, the mobile terminal 100 in the first state is in a contracted position, and has a smaller size than the mobile terminal 100 in the second state. In addition, the size of the display unit 151 positioned on the front of the mobile terminal 100 is also smaller than in the second state. The mobile terminal 100 in the first state may be extended in a first direction D1 to switch to the second state. In the second state, as shown in FIG. 2(b), the size of the mobile terminal 100 and the size of the display unit 151 positioned on the front of the mobile terminal 100 are larger than in the first state, while the size of the display unit 151 positioned on the rear of the mobile terminal 100 is reduced as shown in FIG. 3(b). That is, a part of the display units 151 positioned on the rear of the mobile terminal 151 in the first state moves to the front of the mobile terminal 100 in the second state.

In the following description, the direction in which the mobile terminal 100 and the display unit 151 thereof are extended or enlarged is defined as a first direction D1, and the direction in which the mobile terminal contracts or retracts or is reduced to switch from the second state to the first state is defined as a second direction D2. A direction perpendicular to the first and second directions D1 and D2 is defined as a third and fourth directions. Description will be made on the assumption that the first and second directions are horizontal directions and the third and fourth directions are vertical directions. However, depending on the arrangement of the mobile terminal 100, the first and second directions may be vertical directions and the third direction may be a horizontal direction.

As such, a flexible display unit 151 which is bendable may be used as the display unit such that the position of the display unit may be varied. The flexible display unit 151 may be a display unit capable of maintaining a flat state like a conventional flat panel display and capable of warping, bending, folding, twisting, or rolling like paper. The flexible display unit 151 refers to a display which is manufactured on a thin and flexible substrate and is thus lightweight and robust as not to be easily broken. The flexible display unit according the present disclosure may be bent in a specific direction, and may be arranged such that the curvature thereof may change in the first direction.

In addition, an electronic paper is a display technology to which properties of general ink are applied. The electronic paper may be different from the conventional flat panel display in using reflected light. The electronic paper may change information using a twisted ball or electrophoresis using a capsule.

In a state in which the flexible display unit 151 is not deformed (e.g., a state of having an infinite curvature radius, hereinafter referred to as a basic state), a display region of the flexible display unit 151 becomes flat. In a state in which the flexible display unit 151 is deformed by an external force from the basic state (e.g., a state of having a finite radius of curvature, hereinafter referred to as a deformed state), the display region may become a curved face. As shown, information displayed in the deformation state may be visual information output on the curved face. Such visual information is implemented by independently controlling light emission of sub-pixels arranged in a matrix. The sub-pixel refers to a minimum unit for implementing one color. When external force is applied to the flexible display unit 151, the flexible display unit 151 may be deformed to switch from the default state, which is the flat state, to a bent state, which is not the flat state.

The flexible display unit 151 may be combined with a touch sensor to implement a flexible touch screen. When a touch is made on the flexible touch screen, the controller 180 (see FIG. 1 ) may perform control corresponding to such touch input. The flexible touch screen may be configured to detect the touch input in the deformed state as well as in the basic state.

The touch sensor detects the touch (or touch input) applied on the touch screen using at least one of various touch schemes such as a resistive film scheme, a capacitance scheme, an infrared scheme, an ultrasonic wave scheme, a magnetic field scheme, and the like.

As an example, the touch sensor may be configured to convert a change in pressure applied on a specific portion of the touch screen, capacitance generated at the specific portion, or the like into an electrical input signal. The touch sensor may be configured such that a touch object applying a touch on the touch screen may detect touched position and area on the touch sensor, a pressure during the touch, a capacitance during the touch, and the like.

Further, the mobile terminal 100 may have a deformation detection means for detecting the deformation of the flexible display unit 151. Such deformation detection means may be included in the sensing unit 140 (see FIG. 1 ).

The deformation detection means may be disposed in the flexible display unit 151 or a case (first to second frames 101 to 102 to be described later) to detect information related to the deformation of the flexible display unit 151. In this connection, the information related to the deformation may include a direction in which the flexible display unit 151 is deformed, a degree of the deformation, a deformed position, a deformed time, an acceleration at which the deformed flexible display unit 151 is restored, and the like. In addition, the information related to the deformation may include various kinds of information that may be detected due to the bending of the flexible display unit 151.

In addition, the controller 180 may change information displayed on the flexible display unit 151 or generate a control signal for controlling a function of the mobile terminal 100 based on the information related to the deformation of the flexible display unit 151 detected by the deformation detection means.

The deformation of the flexible display unit 151 may vary depending on the positions of the first frame 101 and the second frame 102. As shown in FIG. 2 , since the bending position on the flexible display unit 151 is determined according to the positions of the first frame and the second frame, the bending deformation position of the flexible display unit 151 and the area thereof positioned on the front may be calculated based on the positions of the first frame 101 and the first frame 102 in place of the deformation detection means of the flexible display unit 151.

The state conversion (first or second state) of the flexible display unit 151, i.e., the size change at the front and rear faces of the mobile terminal 100 of the display unit 151 based on the size change of the mobile terminal 100 may be performed manually by a force applied by the user, but may be not limited to such manual scheme. For example, when the mobile terminal 100 or the flexible display unit 151 is in the first state, the mobile terminal 100 or the flexible display unit 151 may be converted into the second state by the user or an application command without the external force applied by the user. As such, in order for the flexible display unit 151 to be automatically deformed without the external force, the mobile terminal 100 may include a driving unit 200, which will be described later.

The flexible display unit 151 of the present disclosure is bent 180 degrees by rolling around a side portion of the mobile terminal 100 facing in the first direction. Accordingly, based on the side portion of the mobile terminal 100, a part of the flexible display unit 151 is disposed on the front of the mobile terminal 100, and the other part of the flexible display unit 151 is disposed on the rear of the mobile terminal 100. For simplicity, the part of the flexible display unit 151 positioned on the front is called a front face, and the other part of the flexible display unit 151 positioned on the rear is called a rear face. As illustrated in FIG. 2 , the mobile terminal may extend in the first direction or contract in the second direction opposite to the first direction. In this case, the area of the flexible display unit 151 positioned on the front changes. That is, the sizes of the front face and the rear face may be changed according to a change in the state of the mobile terminal.

The part of the flexible display unit 151 positioned on the front of the mobile terminal 100 may be immovably fixed to the front surface of the first frame 101, and the other part thereof positioned on the rear of the mobile terminal 100 may be movably arranged on the rear of the mobile terminal 100.

In addition, the flexible display unit 151 may be rolled on or released at the side portion in the first direction of mobile terminal. Accordingly, the rear face of the display unit 151 moves, so that the size of the front face of the display unit 151 may be adjusted. Since the size of the flexible display unit 151 is determined and the flexible display unit 151 is formed of one continuous body, an area of rear face of the display unit 151 decreases as an area of the front face of the display unit 151 increases. Such a display unit 151 may be rolled in a second frame 102, which is movable relative to a first frame 101 to be described later, more correctly, on one of sides of the second frame 102. The display unit 151 may be withdrawn or pulled out from or inserted or pushed into the second frame 102 while being rolled in the second frame 102 along a moving direction of the second frame 102 to adjust the area of the display unit 151 on the front face of the mobile terminal 100. Such operation will be described in more detail below along with other relevant components of the mobile terminal 100.

Typically, an antenna is disposed in the case or the housing of the mobile terminal 100, but a portion where the antenna is installed in the case or the housing may be limited because of the flexible display unit 151 that covers not only the front face of the mobile terminal 100 but also the rear face thereof. For this reason, the antenna may be implemented on the flexible display unit 151. An antenna on display (AOD) is an antenna in which a transparent film is formed by stacking an electrode layer and a dielectric layer that have patterns engraved thereon, respectively. The antenna on display may be implemented thinner than an antenna implemented using a laser direct structuring (LDS) technology using a conventional copper nickel plating scheme, so that the antenna on display may not be exposed to the outside without affecting a thickness. In addition, the antenna on display may transmit and receive a signal directly to or from the display unit 151. Accordingly, the antenna on display may be used in the mobile terminal 100 in which the display unit 151 is located on the both faces of the mobile terminal 100 as in the present disclosure.

FIGS. 4 and 5 are exploded perspective views of the mobile terminal in accordance with an embodiment. FIG. 4 is an exploded perspective view of the mobile terminal as viewed from the front side, and FIG. 5 is an exploded perspective view of the mobile terminal as viewed from the rear side.

The mobile terminal 100 of the present disclosure includes frames 101 and 102 in which components are mounted, and the frames 101 and 102 of the present disclosure may vary in size in the first direction as shown in FIG. 2 . One or more frames 101 and 102 move relative to each other, and sizes thereof may vary in the first direction. Electronic components are mounted in the frames 101 and 102, and the flexible display unit 151 is located out of the frames 101 and 102.

Since the mobile terminal 100 of the present disclosure includes the flexible display unit 151, the flexible display unit 151 may be combined in a form surrounding front faces and rear faces of the frames 101 and 102. The frame may include the first frame 101 and the second frame 102 moving in the first direction with respect to the first frame 101. The first frame 101 and the second frame 102 include front portions, a rear portions, and side portions, respectively, and are coupled to each other.

First, the first frame 101 corresponds to a main body of the mobile terminal 100, and may have a space between the first front portion 1011 and the first rear portion 1012 therein for accommodating various components. In addition, the first frame 101 may accommodate the second frame 102 movably coupled to the first frame 101 in such a space. More specifically, as shown in FIGS. 2 and 5 , the first frame 101 may include a first front portion 1011 disposed at a front portion of the mobile terminal 100 and supporting the front face of the display unit 151 and a first rear portion 1012 disposed at a rear portion of the mobile terminal and on which various components are mounted. A front deco 1016 may cover front edges of the first area 151 a to protect the edges of the first area 151 a.

The first front portion 1011 and the first rear portion 1012 may be spaced apart from each other at a predetermined spacing to define a predetermined space therebetween, and may be connected to each other by a first side portion 1013. The first side portion 1013 may be integrally formed with the first rear portion 1012 or the first front portion 1011. The camera 121, the audio output module 152, and the input/output terminal, the controller 180, and the power supply unit 190 may be accommodated as components of the mobile terminal 100 in the space in the first frame 101. For example, the controller 180 may be a circuit board 181 including a processor and an electronic circuit for controlling the operation of the mobile terminal, and the power supply unit 190 may be a battery 191 and related components. In addition, the driving unit 200 that controls the slide movement of the second frame 102, which will be described later, may also be accommodated in the first frame 101.

As described above, the display unit 151 has the continuous body, and thus, may be disposed on both the front face and the rear face of the mobile terminal 100 while being rolled in the mobile terminal 100. The display unit 151 may include the front face positioned at the front face of the mobile terminal 100, the rear face positioned at the rear face of the mobile terminal 100, and the side face positioned between the front face and the rear face thereof and surrounding the side face of the mobile terminal. The front face and the rear face of the display unit 151 are flat, and the side face of the display unit 151 may form a curved face. The flexible display unit 151 may be damaged when being bent at an angle. Thus, the flexible display unit 151 may be formed to be bent with a predetermined curvature at the side face.

The display unit 151 may be divided into a fixed portion 151 a and 151 b and a variable portion 151 c. The fixed portion 151 a and 151 b means a portion fixed to the frame. Because of being fixed to the frame, the fixed portion 151 a and 151 b maintains a constant shape without changing a bending degree. On the other hand, the variable portion 151 c means a portion in which a bending angle or a position of the bent portion changes. The variable portion 151 c in which the position or bending angle of the bent portion changes requires a structure for supporting a rear face of the variable portion 151 c in response to the change.

The fixed portion 151 a, 151 b is coupled to the first frame of the display unit and is always positioned on the front face of the display unit to form a portion of the front face of the display unit. The variable portion 151 c includes a side face located at a side portion of the mobile terminal, and a position of the side face varies depending on the position of the second frame. Based on a side face, an area of a portion disposed on the front face of the display unit and an area of a portion disposed on the rear face of the display unit vary. That is, a portion of the variable portion 151 c may be the front face and another portion of the variable portion 151 c may be the rear face based on the first and second states. The variable portion 151 c is positioned in the first direction with respect to the fixed portion 151 a, 151 b relative to the mobile terminal, and an end of the variable portion 151 c is bent toward the rear face of the mobile terminal and slides on the rear face of the second frame.

The end of the variable portion of the display unit is coupled with a slide frame that guides the variable portion to slide move on the rear face of the second frame, and the slide frame moves in the first direction at the same time as the second frame moves in the first direction. As a result, a moving distance of the slide frame with respect to the first frame is twice as a moving distance of the second frame with respect to the first frame. Further, as shown in FIG. 3 , the first rear portion 1012 of the mobile terminal 100 includes an exposed rear portion 1015 that is exposed to the outside without being covered by the display unit 151 even in the first state. The physical input unit 120 for the manipulation of the mobile terminal 100 such as various buttons, switches, the camera 121, and a flash, and the sensing unit 140 such as the proximity sensor 141 or a fingerprint sensor may be arranged on the exposed rear portion 1015. The first rear portion 1012 except for the exposed rear portion 1015 may be covered by the display unit 151 in the first state as shown in FIG. 3(a), and may be exposed rearward in the second state as shown in FIG. 3(b).

In a conventional bar-shaped terminal, a display unit is provided only on a front face of the terminal. Therefore, a main camera is placed on a rear face of the terminal in order for the user to capture an object at an opposite side while looking through the display unit. On the other hand, an additional auxiliary camera is required to be disposed on the front face of the terminal in order for the user to capture himself or herself while viewing himself or herself through the display unit.

In the mobile terminal 100 of the present disclosure, on the other hand, the display unit 151 is arranged on both the front and rear of the mobile terminal 100. Accordingly, when a user photographs himself, a portion of the display unit 151 positioned on the same surface as the camera 121, that is, the rear face of the display unit 151 may be used. When the user takes a photograph of an object around the user, a portion of the display unit 151 on the side facing away from the camera 121, that is, the front face of the display unit 151 may be used. For this reason, the mobile terminal 100 may take a photograph of the user or an object located around the user using one camera 121. The camera may include a plurality of cameras having different angles of view, such as wide angle, ultra wide angle, and telephoto angle. Not only the camera but also a proximity sensor and an audio output unit may be disposed on the exposed rear portion 1015, and an antenna may be installed on the rear portion 1015. The rear portion 1015 may be used to protect the camera, the sensor, or the like on the exposed rear portion 1015 and not to deteriorate the exterior design. A portion of the rear portion 1015 corresponding to the camera 121 or the sensor 140 may be configured to be transparent, and the other portion thereof may have a predetermined pattern or color in consideration of design aspects without exposing internal parts.

The first side portion 1013 may extend along the edges of the first front portion 1011 and the first rear portion 1012 to surround the circumference of the first frame 101 and may define the appearance of the mobile terminal 100. However, as mentioned above, the second frame 102 is accommodated in and movably coupled to the first frame 101, and therefore a portion of the first frame 101 needs to be open to allow movement of the second frame 102 relative to the first frame 101. As an example, as best shown in FIG. 2 , the second frame 102 may be movably coupled to a side of the first frame 101 facing in the first direction, and accordingly the first side portion 1013 may not be formed on the lateral surface facing in the first direction such that the lateral surface is open. Since the first side portion 1013 is exposed to the outside of the mobile terminal 100, the interface unit 160 for connecting a power port or an ear jack or the user input unit 120, such as a volume control button, may be disposed on the first side portion 1013. When the first side portion 1013 contains a metal material, the first side portion 1013 may serve as an antenna.

The second frame 102 may include a second front portion 1021 disposed at the front portion of the mobile terminal 100 and a second rear portion 1022 disposed at the rear portion of the mobile terminal 100. Like the first front portion 1011 and the first rear portion 1012 of the first frame 101, the second front portion 1021 and the second rear portion 1022 may be formed of plate-shaped members that are generally flat. In addition, the second frame 102 also accommodates various components, and must not interfere with the components accommodated in the first frame 101 during the movement. Accordingly, the second front portion 1021 and the second rear portion 1022 may be coupled to each other in a state of being spaced apart from each other to define a predetermined space therebetween, and may have shapes that do not interfere with the components in the first frame 101.

FIG. 6 is a side view of the mobile terminal as viewed from a third direction. FIG. 6 shows the first side portion 1013 of the first frame 101 and a second side portion 1023 of the second frame 102. Since the flexible display unit 151 is positioned at an end of the second frame 102 facing in the first direction, the end of the second frame 102 facing in the first direction should not be exposed to the outside. An end of the second frame 102 facing in the second direction should be open so as not to interfere with the first frame 101. In the first state, the second side portion 1023 of the second frame 102, which is positioned on the side facing in the third direction (which refers to the upward or downward direction in the drawing or may include both the upward and downward directions), may not be exposed to the outside because it overlaps the first side portion 1013 of the first frame. However, in the second state, it may be exposed to the outside because the second frame 102 is drawn out.

In addition, the display unit 151 may be bent 180 degrees while being rolled in the second frame 102 to be disposed on both the front face and the rear face of the mobile terminal 100. For such an arrangement of the display unit 151, the second frame 102 may include a roller 210 rotatably disposed therein. The roller 210 may be disposed at any position inside the second frame 102. However, the display unit 151 should be spread flat on the front face and the rear face of the mobile terminal 100 to provide a good quality screen to the user. Further, for such spread, a proper tension must be provided on the display unit 151. In order to provide the proper tension, the roller 210 may be disposed at a first directional end of the second frame 102. The roller 210 may extend in the third direction, and may be rotatably coupled to the second frame 102.

The display unit 151 may be rolled around the roller 210 while being gently bent with a predetermined curvature. The flexible display unit 151 may include a first face on which a video is output and exposed to the outside and an inner face facing the frame at the opposite side. The roller 210 may be installed to rotate freely in the second frame 102 while being in contact with the inner face of the display unit 151. Accordingly, the roller 210 may actually move the display unit 151 in a lateral direction of the mobile terminal 100, that is, in a direction perpendicular to a longitudinal direction. As will be described later, when the second frame 102 slides, because of the tension applied by the second frame 102, the display unit 151 moves to the front face or the rear face of the mobile terminal 100 in different directions (i.e., the first direction D1 or the second direction D2) relative to the second frame 102. The roller 210 may guide such movement while rotating.

The roller 210 may be disposed adjacent to the end of the second frame 102 that faces in the first direction. A side frame 1024 may be disposed at the end of the second frame 102 facing in the first direction to prevent damage to the display unit 151 rolled around the roller 210.

The side frame 1024 may extend in the longitudinal direction (the third direction) of the second frame 102 to cover the side portion facing in the first direction, thereby protecting the roller 210 and the display unit 151 rolled therearound.

An inner surface of the side frame may include a curved surface corresponding to the curvature of the side portion.

The side frame 1024 may substantially define the appearance of the mobile terminal 100 in cooperation with the first side portion 1013 of the first frame 101. In addition, the side portion of the second frame 102 that faces in the second direction may be omitted to minimize interference with the components arranged in the first frame 101 during movement.

During the expansion and the contraction in such first and second directions D1 and D2, the second frame 102 may overlap the first frame 101, more precisely, the first front portion 1011 and the first rear portion 1012 thereof so as not to interfere with the first frame 101. More specifically, the display unit 151 may be coupled to and supported by the first front portion 1011 of the first frame 101, as described above. Accordingly, the display unit 151 does not need to be additionally supported by the second front portion 1021 of the second frame 102. Rather, when the second front portion 1021 is interposed between the first front portion 1011 and the display unit 151, the display unit 151 may be deformed or damaged because of friction with the second front portion 1021, which is repeatedly moved. Thus, the second front portion 1021 may be disposed below the first front portion 1011, or may be interposed between two first front portions 1011. The second rear portion 1022 of the second frame 102 may be disposed rearward of the first rear portion 1012 of the first frame 101. That is, the front face of the second rear portion 1022 may face the rear face of the first rear portion 1012. In addition, the rear face of the first rear portion 1012 may be in contact with the front face of the second rear portion 1022 to stably support the movement of the second frame 102. Because of such arrangement, the second rear portion 1022 may be exposed to the outside of the first frame, more precisely, of the first rear portion 1012, and may be coupled to the display unit 151.

In addition, the second frame 102 may extend and contract in the first and second directions D1 and D2 to change the size of the mobile terminal 100, particularly, to extend or contract the front face of the mobile terminal 100. Thus, the display unit 151 must move by such extended or reduced front face size to obtain the intended first and second states. However, when being fixed to the second frame 102, the display unit 151 may not be moved smoothly to be adapted for the front face of the mobile terminal 100 that is extended or contracted. For this reason, the display unit 151 may be movably coupled to the second frame 102.

More specifically, the display unit 151 may include a first region 151 a disposed on the front of the mobile terminal 100, a second region 151 b coupled to a slide frame 103 positioned on the rear of the mobile terminal 100, and a third region 151 c located between the first region 151 a and the second region 151 b and bent around the roller 210. The third region 151 c may move to the front or the rear according to change in the state of the mobile terminal 100. The slide frame 103 may be formed of a plate-shaped member extending in the longitudinal direction (the third direction) of the mobile terminal 100, and may be coupled to the second rear portion 1022 so as to be movable in the first and second directions D1 and D2.

The first to third regions 151 a, 151 b, and 151 c may be connected to each other, and may form a continuous body of the display unit 151. In addition, as described above, for the movement of the third region 151 c toward the front face or the rear face of the mobile terminal 100 depending on the moving direction of the second frame 102, the first region 151 a may be fixed so as not to move to the front face of the mobile terminal 100, and the second region 151 b may be provided to be movable on the rear face of the mobile terminal. Such configuration of the display unit 151 will be described in more detail below.

The first region 151 a may be disposed on the front face of the mobile terminal 100, more specifically, the first frame 101, that is, on the front face of the first front portion 1011. The first region 151 a is fixed to the first frame 101, that is, the front face of the first front portion 1011 so as not to be moved during the movement of the second frame 102, and thus, the first region 151 a may always be exposed to the front face of the mobile terminal 100.

The third region 151 c may be adjacent to the first region 151 a in a direction of a second end 151 e. The third region 151 c may extend into the second frame 102 and be rolled on the roller 210. The third region 151 c may extend out of the second frame 102 and partially cover the second frame 102, that is, the rear front of the second rear portion 1022. Since the second frame 102, i.e., the second rear portion 1022 is adjacent to the first frame 101, i.e., the first rear portion 1012, and the first and second frames 101 and 102 form the rear case of the mobile terminal 100, it may be said that the third region 151 c is also disposed on the rear front of the first frame 101.

The second region 151 b may be adjacent to the third region 151 c and may be disposed on the rear face of the mobile terminal 100, more specifically, on the second frame 102, that is, the rear face of the second rear portion 1022 thereof. The second region 151 b may be coupled to the slide frame 103 without being directly coupled to the second frame 102.

As a result, the first region 151 a may be disposed on the front face of the mobile terminal 100 and may be always exposed to the front face regardless of the movement of the second frame 102, and the second region 151 b may be disposed on the rear face of the mobile terminal 100 and may be always exposed to the rear face regardless of the movement of the second frame 102. In addition, the third region 151 c may be disposed between the first and second regions 151 a and 151 b, and may be selectively placed on the front face or the rear face of the mobile terminal 100 depending on the moving directions D1 and D2 of the second frame 102.

Because of such selective placement of the third region 151 c, the first rear portion 1012 of the first frame 101 may be exposed to the outside of the mobile terminal 100 because the first rear portion 1012 is covered by the second and third regions 151 b and 151 c and the second rear portion 1022 of the display unit 151 in the first state, but, in the second state, the third region 151 c moves to the front face of the mobile terminal 100 and the second rear portion 1022 also moves in the first direction D1. In addition, the second front portion 1021 of the second frame 102 is hidden by the first front portion 1011 of the first frame 101 in the first state, but, in the second state, moves out of the first frame 101 to support the third region 151 c of the display unit 151 disposed on the front face of the mobile terminal 100.

In order to prevent the second front portion 1021 from affecting the internal components during the slide movement, a separating plate 1017 may be further disposed rearward of the second front portion 1021 and fastened with the first front portion 1011. The second front portion 1021 may move between the first front portion 1011 and the separating plate 1017 based on the slide movement of the second frame.

However, the third region 151 c may be rolled on the roller 210 and bent in the second frame 102. When converting from the first state to the second state, the third region 151 c may extend from the second frame 102 to the front face of the mobile terminal 100 while being rolled on the roller 210 in one direction. On the other hand, when converting from the second state to the first state, the third region 151 c may be retracted from the front face of the mobile terminal 100 to the second frame 102 while being rolled on the roller 210 in the opposite direction, and at the same time, may return to the rear face of the mobile terminal 100 from the second frame 102.

A specific location of the foldable mobile terminal in a form of being spread like a book is easily damaged because only the specific location is folded repeatedly. On the other hand, the deformed portion of the flexible display unit 151, that is, a portion rolled on the roller 210, may vary based on the first and second states of the mobile terminal 100, that is, the movement of the second frame 102. Accordingly, the mobile terminal 100 of the present disclosure may significantly reduce deformation and fatigue repeatedly applied to a specific portion of the display unit 151, thereby preventing damage to the display unit 151.

Based on the above-described configuration, overall operations of the mobile terminal 100 will be described as follows. As an example, the state conversion may be performed manually by the user, and an operation of the mobile terminal 100 during such manual state conversion will be described. However, operations of the first to third frames 101 to 103 and the display unit 151, which will be described below, may be performed in the same manner when a power source other than a user’s force is used, for example, when the driving unit 200 to be described below is applied.

A rear face cover 1025 may be further disposed on a rear face of the second rear portion 1022 such that the rear face of the display unit positioned on the rear face of the mobile terminal 100 is not exposed to the outside. The rear face of the display unit may be used in the first state when the rear face cover 1025 uses a transparent material, and the rear face of the display unit may be covered such that the movement of the slide frame 103 is not exposed when the rear face cover 1025 uses an opaque material. That is, the second region and the third region of the slide frame 103 and the display unit 151 may move in the first direction and in the second direction in a space between the second rear portion 1022 and the rear face cover 1025.

FIG. 7 is a view showing a driving unit 200 of the mobile terminal 100 in accordance with an embodiment. FIG. 7(a) shows the first state and FIG. 7(b) shows the second state. The mobile terminal 100 of the present disclosure may be switched between the states in a manner in which a user manually pulls the second frame 102 in the first direction D1 or pushes the same in the second direction D2 with respect to the first frame 101. However, in the manual method, applying excessive force to the body of the mobile terminal 100 may damage the mobile terminal 100. Accordingly, a driving unit 200 employing a motor 201 may be further provided to cause the second frame 102 to stably move without distortion.

As the motor 201, a motor 201 configured to provide rotational force as shown in FIG. 7 , or a linear motor 201 configured to make linear motion may be used. The motor 201 configured to provide the rotational force should have a large diameter to provide large force. Two motors 201 may be used as shown in FIG. 7 to provide driving force of a predetermined magnitude or more in the limited space of the mobile terminal 100 without increasing the thickness.

If the second frame 102 is moved excessively fast, damage or malfunction may occur. Accordingly, a planetary gear configured to decrease the speed of the motor 201 to ensure movement at a stable speed may be further provided. The planetary gear 202 serves to amplify or attenuate the number of revolutions of the motor 201 using a plurality of disc gears having different numbers of teeth. The motor 201 may be fixed to the first frame 101 as shown in FIG. 7(a). The position of the motor 201 is fixed even when the second frame 102 moves in the first direction to switch the mobile terminal 100 to the second state, as shown in FIG. 7(b).

Since the second frame 102 linearly moves with respect to the first frame 101 in the first direction or the second direction, rack and pinion gears configured to convert the rotational force of the motor 201 into linear motion may be used. A pinion gear to receive the rotational force of the motor 201 may be arranged to engage with a rack gear 205 composed of teeth continuously arranged in the first direction. The pinion gear may be fixed to the first frame 101 together with the motor 201 and the rack gear 205 may be positioned on the second frame 102. Alternatively, the rack gear 205 may be positioned on the first frame 101, and the motor 201 and the pinion gear may be arranged on the second frame 102. Since the motor 201 holds the pinion gear such that the pinion gear does not rotate, the second frame 102 may maintain the first state and the second state. However, when large external force is applied, the second frame 102 may be displaced as the pinion gear rotates.

A stopper (not shown) configured to fix the positions of the second frame 102 or the rack gear 205 and the first frame 101 may be further provided to fix the mobile terminal 100 in the first state or the second state. When electric current flows through the motor 201 to drive the motor 201, the stopper may be released to allow the movement of the second frame 102. When power is not applied to the motor 201 and thus the motor 201 does not rotate, the first frame 101 and the second frame 102 may be fastened such that the positions thereof are fixed.

When a pair of driving units 200 is symmetrically disposed in the vertical direction (the third direction), stable movement may be made. However, to arrange a battery or the like, the driving unit 200 should be arranged biased to one side in consideration of the limited mounting space of the mobile terminal 100 as shown in FIG. 7(a). According to such asymmetric arrangement of the driving unit 200, the second frame 102 may be distorted during movement due to a difference in movement speed between the upper end portion and the lower end portion. To address this issue, a linear guide 230 may be further provided.

The linear guide 230 may be disposed at both ends of the mobile terminal 100 facing in the third direction, that is, on the upper and lower sides of the mobile terminal 100, in order to supplement the function of one driving unit 200 biased to one side in the third direction. The linear guide 230 may include a guide rail 231 extending in the first direction and a guide block 232 configured to move along the guide rail 231. The guide rail 231 may be disposed on the first frame 101 and the guide block 232 may be disposed on the second frame 102, or vice versa. In this embodiment, the guide rail 231 may be disposed on the second frame 102 to cover the upper and lower sides of the extended portion of the second frame 102 in the second state.

After the guide block 232 is coupled to the first frame 101 and the guide rail 231 is coupled to the second frame 102, the guide block 232 and the guide rail 231 may be slidably fastened to each other. However, for convenience of the fastening, the guide block 232 and the guide rail 231 fastened to each other. Then, the guide block 232 may be first fixed to the first frame 101, and then the second frame 102 may be coupled to the guide rail 231.

The guide block 232 may be provided with a guide groove into which the guide rail 231 is inserted. Alternatively, the guide rail 231 may be provided with a rail groove into which a portion of the guide block 232 is inserted. The fastening portions of the guide rail 231 and the guide block 232 may be formed to be bumpy. Accordingly, movement in the first direction or the second direction may be made without displacement in the thickness direction of the mobile terminal 100. In order to reduce friction between the guide block 232 and the guide rail 231, a self-lubricating member having high wear resistance and low friction resistance, such as a bearing or polyoxymethylene (POM), may be added to the inside of the guide groove.

FIG. 8 is a cross-sectional view taken along lines A-A and B-B in FIG. 2 . As illustrated in FIG. 2 , when the second frame 102 switches to the second state by moving in the first direction, the third region 151 c positioned on the rear side moves to the front, and thus a structure to support the rear surface of the third region 151 c moved to the front is required. The second front portion 1021 positioned on the front surface of the second frame 102 may be positioned on the rear surface of the third region 151 c in the second state. However, in the first state, the second front portion 1021 is disposed to overlap the first front portion 1011 of the first frame 101, and accordingly the first front portion 1011 and the second front portion 1021 form a step. A boundary is formed between the first region 151 a and the third region 151 c of the flexible display unit 151 by the step formed by the first front portion 1011 and the second front portion 1021. A rolling hinge 104 may be used as a support structure to fill the gap between the second front portion 1021 and the third region 151 c of the flexible display unit 151.

The rolling hinge 104 may be positioned on the rear surface of the flexible display unit 151, and have a thickness corresponding to the gap between the second front portion 1021 and the flexible display unit 151 in the second state. As shown in FIG. 8(a), in the first state, the rolling hinge 104 is rolled around the roller 210 and is positioned on the lateral side and rear side of the mobile terminal 100. The flexible display unit 151 and the rolling hinge 104 may be positioned between the second rear portion of the second frame 102 and a rear cover 1025 provided to cover the rear face of the display unit 151. As shown in FIG. 8(b), when switch to the second state occurs, the rolling hinge 104 may move to the front and the rolling hinge 104 may be positioned on the front portion of the second frame 102.

The third region 151 c of the display unit 151 in which the rolling hinge 104 is positioned is a portion where bending deformation occurs when switch from the first state to the second state occurs. Accordingly, the rolling hinge 104 may be deformed according to deformation of the third region 151 c. Here, the rolling hinge 104 is required to have a predetermined stiffness to maintain the flat state when the flexible display unit 151 is positioned on the front or rear of the mobile terminal. That is, the rolling hinge 104 needs a structure capable of maintaining the flat state in the third direction and performing bending deformation in the first direction.

FIG. 9 is a view illustrating a display unit 151 and a rolling hinge 104 of the mobile terminal 100 in accordance with an embodiment. The rolling hinge 104 may include multiple support bars 1041 extending in the third direction. The multiple support bars 1041 may be arranged side by side in the first direction and spaced apart from each other by a predetermined distance. Accordingly, even when the flexible display unit 151 is rolled around the roller 210 and is thus bent, interference between the support bars 1041 may be avoided. The support bars 1041 may be implemented with an injection molding material having a predetermined thickness for stiffness, and may include materials such as SUS or ferrosilicon (FeSi).

The multiple support bars 1041 may be directly attached to the rear surface of the display unit 151. However, this operation may take a long time and produce a lot of defects, resulting in poor productivity. In addition, directly processing the display unit 151 is highly likely to damage the display unit 151. Therefore, a rolling sheet 1045 to fix the multiple support bars 1041 may be further provided. The rolling sheet 1045 may include a metal material, and may employ a superelastic material that is bending-deformable and capable of recovering the flat state after the bending deformation. For example, a superelastic metal sheet such as a thin STS sheet of 0.05 mm or less may be used. An adhesive tape may be attached to both surfaces of the rolling sheet 1045 to bond the rolling sheet 1045 to the support bars 1041 and bond the rear surface of the display unit 151 to the rolling sheet 1045.

The rolling sheet 1045 may be provided with a kerf pattern in which multiple grooves extending in the third direction are formed in the first direction. The grooves in the kerf pattern may be formed between the multiple support bars 1041. The grooves may be formed on a surface of the rolling sheet 1045 to which the support bars 1041 are bonded. The kerf pattern may be formed in a wedge shape that is formed by being gradually narrowed from the surface portion of the rolling sheet 1045.

Instead of the rolling sheet 1045, an elastic material such as silicone may be disposed between the support bars 1041 to join neighboring support bars 1041. In this case, the angle between the support bars 1041 may be varied. The elastic connector may be bent at a position corresponding to the roller 210. When positioned on the front or rear of the mobile terminal, the elastic connector may be unfolded such that the support bars 1041 are disposed forming a flat surface.

The support bars 1041 may form a flat surface corresponding to the rear surface of the display unit 151. Alternatively, as shown in FIG. 8(b), the support bars 1041 may be formed in a shape having a predetermined curvature. The curved support bars 1041 may closely contact the curved surface of the roller 210 when the rolling hinge 104 is rolled around the roller 210. Alternatively, one surface of the support bars 1041 in contact with the display unit 151 maintains a flat state, and the other surface thereof on the opposite side may include a curved surface corresponding to the curvature of the roller 210. In this case, the support bars 1041 may be thick at the ends thereof facing in the first and second directions and have the thinnest portion in the middle thereof.

The rolling hinge 104 may be disposed at a position corresponding to the third region 151 c and is rolled and bent around the roller 210. Thus, the rolling hinge 104 may span over the front and rear surfaces. The rolling hinge 104 is connected to the first front portion 1011 of the first frame 101 on the front side and connected to the slide frame 103 on the rear side. In order for the flexible display unit 151 to form a continuous surface without a step, the first front portion 1011 of the first frame 101 positioned on the rear surface of the first region 151 a, the slide frame 103 positioned on the rear surface of the second region 151 b, and the rolling hinge 104 positioned on the rear surface of the third region 151 c may be arranged such that the surfaces thereof in contact with the display unit 151 are at the same height. In particular, since the slide frame 103 moves on the rear of the mobile terminal 100 and moves in the same space as the rolling hinge 104, the rolling hinge 104 may have a thickness corresponding to the thickness of the slide frame 103.

FIG. 10 is a view illustrating an issue raised in an extendable mobile terminal 100. The figure shows the end of the second frame 102 facing in the third direction when the second frame 102 positioned overlapping the first frame 101 is extended as switching from the first state to the second state occurs. Since the display unit 151 contains a flexible material, the display unit 151 may be bent at a position corresponding to the roller 210. However, when the display unit 151 is positioned on the front of the mobile terminal 100 in the second state, it should be maintained in a flat state. Since the rolling hinge 104 is not fixed to the second frame 102, the display unit 151 may sag downward as shown in FIG. 10(a) or rise upward as shown in FIG. 10(b).

The sagging issue of the display unit 151 (in FIG. 10(a)) may be addressed when the support bars 1041 of the rolling hinge 104 described above support the rear surface of the third region 151 c of the display unit 151 and the front portion of the second frame 102 supports the support bars 1041. However, in order to address an issue that the display unit 151 moved to the front is not arranged flat but is separated from the second frame 102 as shown in FIG. 10(b), the rolling hinge 104 and the second frame 102 may further include a slide structure 1043, 1027. The slide structures 1043 and 1027 may fasten the rolling hinge 104 (the display unit 151) so as not to be separated from the second frame 102 in the thickness direction of the mobile terminal 100 while allowing the movement thereof only in the first direction or the second direction.

FIGS. 11 to 13 are views showing the slide structures 1043 and 1027 provided on the rolling hinge 104 and the second frame 102. FIG. 11 is a cross-sectional view taken along lines C-C and D-D in FIG. 2 , FIG. 12 is a cross-sectional view taken along lines E-E and F-F in FIG. 10 , and FIG. 13 is a view showing an expanded side portion 1042 and a guide hook 1043 of the mobile terminal 100 in accordance with an embodiment.

As shown in FIG. 13 , the rolling hinge 104 may include a slide hook 1043 protruding toward the second side portion 1023 positioned on the side of the second frame 102 facing in the third direction. As shown in FIG. 11 , the second side portion 1023 of the second frame 102 may include a slide rail 1027 into which the slide hook 1043 is movably inserted. FIG. 11 shows the slide rail 1027 formed on the second side portion 1023 of the second frame 102. The slide rail 1027 may include a pair of horizontal portions 1027 a and 1027 b arranged side by side in a thickness direction and a curved portion 1027 c connecting ends of the horizontal portions 1027 a and 1027 b facing in the first direction. The pair of horizontal portions 1027 a and 1027 b and the curved portion 1027 c may form a U shape, and the slide hook 1043 may move along the slide rail 1027.

In the first state, the slide hook 1043 may be positioned in the horizontal portion 1027 a, 1027 b positioned on the rear side, as shown in FIG. 11(a). In the second state, the slide hook 1043 may be moved to the horizontal portion 1027 a, 1027 b positioned on the front side, as shown in FIG. 11(b). When moved from the rear horizontal portion 1027 a, 1027 b to the front horizontal portion 1027 a, 1027 b, the slide hook 1043 may pass through the curved portion 1027 c. When the slide hooks 1043 pass through the curved portion 1027 c, the rolling hinge 104 may be bent and the space between the slide hooks 1043 may be narrowed.

The slide rail 1041 along which the slide hook 1043 moves may guide the movement of the slide hook 1043 and the movement of the slide frame 103 simultaneously. Since the slide frame 103 is also disposed adjacent to the support bars, a slide hook 1033 protruding from the slide frame 103 may be further provided.

FIG. 12(a) shows the second frame 102 in the first state in which the first frame 101 and the second frame 102 overlap each other, and FIG. 12(b) shows the second frame 102 moved from the first frame 101 in the first direction in the second state. As shown in FIG. 12(a), the support bars 1041 and the slide hooks 1043 are positioned on the rear in the first state. In the second state, as shown in FIG. 12(b), the support bars 1041 and the slide hooks 1043 are positioned on the front. The distance from the front face of the display unit 151 to the front horizontal portions 1027 a and 1027 b may be equal to the distance from the rear face of the display unit 151 to the rear horizontal portions 1027 a and 1027 b.

When large friction occurs during movement of the slide hooks 1043 along the slide rail 1027, a large load may be applied to the driving unit 200, thereby generating frictional noise or affecting the durability of the product. A self-lubricating member having high abrasion resistance and low friction resistance, such as polyoxymethylene (POM), may be used to facilitate the movement of the slide hooks 1043 on the slide rail 1027. By forming the slide hooks 1043 in a cylindrical shape, the area thereof in contact with the slide rail 1027 may be minimized.

As illustrated in FIG. 13 , a slide roller 1044 fitted onto the slide hook 1043 may be further provided. The slide roller 1044 may be fitted onto the cylindrical slide hook 1043 to rotate about an axis extending in a direction in which the slide hook 1043 protrudes. The slide roller 1044 may rotate when the slide hook 1043 moves along the slide rail 1027, thereby reducing friction generated between the slide roller 1044 and the slide rail 1027.

A bearing structure may help to reduce the friction, but it may increase the overall size. For this reason, a simple ring-shaped slide roller 1044 may be used. A fastening groove 1043 a and a fastening protrusion 1044 a may be further provided to prevent the slide roller 1044 from being separated from the slide hook 1043. When the fastening protrusion 1044 a is inserted into the fastening groove 1043 a, the fastening groove 1043 a formed on the outer circumferential surface of the slide hook 1043 in a ring shape and the ring-shaped fastening protrusion 1044 a protruding from the inner surface of the slide roller 1044 are fastened to each other.

The second side portion 1023 of the second frame 102 is disposed overlapping the first side portion 1013 of the first frame 101 in the first state, and is exposed to the outside in the second state. Since the second side portion 1023 is positioned inside the first side portion 1013 of the first frame 101 in the first state, it may be difficult to connect the interface unit 160, the user input unit 123, the audio output unit 152, the antenna, and the like, which are positioned on the first side portion 1013, to the printed circuit board 181, which is positioned inside.

The second side portion 1023 may include an opening 1023 a formed by omitting at least a part of the second side portion 1023 to connect the components positioned on the first side portion 1013 to the printed circuit board 181 positioned inside the first frame 101. Through the opening 1023 a, a connector may be arranged between the components positioned on the first side portion 1013 and the printed circuit board. The opening 1023 a may have a shape elongated in the first direction to prevent interference between the connector and the second side portion 1023 of the second frame 102 even when the second frame 102 is moved.

However, in order to prevent the inside of the mobile terminal 100 from being exposed through the opening 1023 a in the second state, an expanded side portion 1042 may be formed at an end of the support bar 1041 to cover the opening 1023 a in the second state. The expanded side portion 1042 may have a larger area than the cross section of the support bar 1041 at the end of the support bar 1041. The slide hook 1043 may be formed on a first expanded side portion 1042 a extending in a direction away from the display unit 151. When the slide hook 1043 is disposed parallel to the support bar 1041, the second side portion 1023 of the second frame 102 should be extended adjacent to the display unit 151, which may make it difficult to form the opening 1023 a. Accordingly, the slide hooks 1043 may be formed at positions spaced apart from the display unit 151 by a predetermined distance. The first expanded side portion 1042 a may be formed in a fan shape to have a width that is reduced as the first expanded side portion 1042 a extends in a direction away from the display unit 151. FIG. 13 is a view showing an embodiment of the rolling hinge 104 of the mobile terminal 100. Since the rolling plates at positions on the curved portion 1027 c of the slide rail 1027 spaced apart from the display portion 151 are disposed adjacent to each other, the first expanded side portion 1042 a may be formed in a fan shape to prevent the rolling plates from overlapping each other.

When the rolling hinge 104 is positioned in the curved portion 1027 c of the slide rail 1027, since neighboring expanded side portions 1042 are close to each other in a portion spaced apart from the display unit 151, i.e., at a position in which the slide hook 1043 is disposed. The expanded side portion 1042 may have the shape of a fan where its width decreases as the expanded side portion 1042 is farther away from the support bar 1041 to prevent an overlap between first expanded portions 1042 a. The expanded side portion 1042 may also extend in the left-right direction, and may thus cover a space between neighboring support bars 1041. The expanded side portion 1042 may further include a second expanded side portion 1042 b forming a step with respect to the first expanded side portion 1042 a as shown in FIG. 13 . The second extension side portion 1042 b may be disposed to overlap the first expanded side portion 1042 a adjacent thereto to cover the space between the support bars 1041. The second expanded side portion 1042 b may have a size corresponding to the thickness-wise size of the opening 1023 a formed in the second side portion 1023 of the second frame 102. The second expanded side portion 1042 b may be formed to be shorter than the first expanded side portion 1042 a on the side spaced apart from the display unit 151. The second expanded side portion 1042 b may be formed to be shorter than the first expanded side portion 1042 a to prevent the second expanded side portions 1042 b from overlapping each other when the rolling plates pass through the curved portion 1027 c of the slide rail 1027. The second expanded side portion 1042 b may be formed to have a size corresponding to the size of the opening 1023 a to cover the space between the first expanded side portions 1042 a to prevent the inside of the second frame 102 from being exposed to the outside. FIG. 14 is a view showing the slide frame 103 and the second frame 102 of the mobile terminal 100. Like the rolling hinge 104, the slide frame 103 is positioned on the rear surface of the display unit 151 and moves together with the display unit 151. The rolling hinge 104 moves to the back and front of the mobile terminal 100, but the slide frame 103 moves only on the back of the mobile terminal 100, that is, on the second rear portion 1022 of the second frame 102. A structure to guide the slide frame 103 to linearly move in the first direction or the second direction without distortion is needed. A guide slot extending in the first direction may be formed in the rear surface of the second frame 102 and the slide frame 103 may be configured to move along the guide slot.

However, since the second side portion 1023 of the second frame 102 includes the slide rail 1027 extending in the first direction as described above, the movement of the slide frame 103 may be guided through the slide rail 1027, into which the slide hook 1043 of the rolling hinge 104 is inserted, without forming a separate guide rail. As shown in FIG. 15 , slide hooks 1033 may be formed at both ends of the slide frame 103 to guide the slide frame 103 to move along the slide rail 1027. The slide hooks 1033 of the slide frame 103 may have a shape similar to that of the slide hook 1043 of the rolling hinge 104. The slide hooks 1033 protrude from the display unit 151 in a direction away from the display unit 151. However, since the slide hooks 1033 of the slide frame 103 do not move to the front, they move only on a first horizontal portion.

Since the slide frame 103 and the rolling hinge 104 move along the slide rail 1027, movement in the first direction and movement in the second direction may be guided stably, and the issue of separation of the display unit 151 from the second frame 102 may be addressed. However, since the slide rail 1027 is positioned at the end facing in the third direction, the middle portion of the slide frame 103 in the third direction may be separated from the second frame 102. To prevent the separation at the middle portion of the slide frame 103 while both ends of the slide frame 103 are fixed to the frame 102, a magnetic material may be used.

FIG. 15 is a graph showing phase distortion in the mobile terminal 100, and FIG. 16 is a conceptual view for explaining causes of the phase distortion of FIG. 15 .

The flexible display unit 151 may include a portion (fixed portion) attached to the first frame 101 and a portion (variable portion) not attached to the first frame 101 or a bending portion. The first region 151 a is fixed to the first frame 101, but the second region 151 b is not fixed to the first frame 101 so that it is capable of bending or moving to the front and rear side.

In FIG. 15 , ①, ②, and ③ respectively show phase distortion in the display unit 151 at the top, middle, and bottom of the fixed portion, and ④, ⑤, and ⑥ respectively show phase distortion in the display unit 151 at the top, center, and bottom of the variable portion. Since the fixed portion is fixed to the first frame 101, the amount of phase distortion is relatively low. In particular, since the center part is more stably attached to the first frame 101 than the top and bottom parts, the amount of phase distortion at the center part is lower than the top and bottom parts.

However, since an end in the second direction, i.e., the left end in the drawing is attached to the first frame 101 while being bent as shown in FIG. 16 , it may have a repulsive force to the flatness of the display unit 151. As a result, phase distortion may occur at the end in the second direction. In addition, the end of the fixed portion facing in the first direction is adjacent to the variable portion, phase distortion may occur thereat due to the deformation of the variable portion.

The rear surface of the variable portion is supported by the rolling hinge 104. However, since the rolling hinge 104 has a deformable structure unlike the frames, the phase distortion at the fixed portion may increase. The phase distortion may increase at a point between the fixed and variable portions where the support structure (e.g., frame or rolling hinge) is partially omitted on the rear surface thereof. Further, the phase distortion may also increase at a point where the variable portion is rolled on the roller 210.

Referring to FIG. 16 , the phase distortion at the end of the fixed portion facing in the second direction, the point between the fixed and variable portions, and the point where the variable portion is rolled on the roller 210 may be convex outward, whereas the phase distortion at the center of the fixed portion attached to the first frame 101 may be reverse to the former distortion.

The phase distortion at the center of the variable portion is similar to that of the fixed portion. A line distinguishing between the support bar 1041 and a portion combined with the support bar 1041 of the rolling hinge 104 on the rear surface may appear on the display unit 151.

To minimize the phase distortion, the display unit 151 needs to be in a tight state. To reduce vertical distortion in the display unit 151, the variable portion of the display unit 151 should be flat.

Since the end of the third region (variable portion) facing in the vertical direction (third direction) is fixed by the liner guide 230, there may be no waviness. However, since there may be waviness in the center thereof facing in the third direction, a rivet rail 1029 or slide rivets 1049 and 1039 may be used to prevent from the second area 151 b or the third area 151 c from separated from the second frame 102.

FIG. 17 is a view showing coupling of the roller 210 and the rolling hinge of the mobile terminal. The rolling hinge 104 includes the plurality of support bars 1041, and the support bars 1041 extend in the third direction and are arranged side by side in the first direction. In order to avoid interference between neighboring support bars 1041 when the display unit 151 is wound around the roller 210, the support bars 1041 are arranged to be spaced apart from each other by a predetermined distance as shown in FIG. 17 , or may have a cross-section in which width decreases in a direction away from the display unit 151.

When the plurality of support bars 1041 are spaced apart from each other or the support bar 1041 decreases in the width toward an end thereof, the plurality of support bars 1041 may serve as rack gears. Teeth 2141 having protrusions, each of which is inserted between two neighboring support bars 1041, may be formed on the roller 210. The roller 210, which has a smooth surface, may not be in close contact with the rolling hinge 104 and may be pushed, causing the display unit 151 to lift.

In the present disclosure, because the teeth 2141 of the roller 210 and the support bars 1041 of the rolling hinge 104 are engaged with each other and moved, the rotation of the roller 210 and the movement of the display unit 151 may be synchronized without misalignment.

A driving force may be provided to the roller 210 itself, but because the motor 201 of the aforementioned driving unit 200 is located on the first frame 101, there is a problem in that a separate motor is required in order to provide the driving force to the roller 210 located on the second frame 102. Because a mounting space of the mobile terminal 100 is limited to have the additional motor, in the present disclosure, an elastic member 213 may be added to the roller 210 to provide a force for assisting the movement of the display unit 151.

FIG. 18 is an exploded perspective view of the roller 210 of the mobile terminal 100, and FIG. 19 is a view showing an order of fastening each component of the roller 210. The roller 210 of the present disclosure includes a fixed shaft 211, a driving shaft 212, a coil spring 213, and a rotating cylinder 214, and is located in a seating portion 1028 (see FIG. 21 ) of the roller 210 located at an end in the first direction of the second frame 102. The fixed shaft 211 is fixed to the seating portion 1028 and does not rotate, and the drive shaft 212 is rotatably coupled to the fixed shaft 211.

One end 2111 of the fixed shaft is fixed to the seating portion 1028, and the seating portion 1028 of the roller 210 may include a fixing hole 10281 into which a screw passing through one end 2111 of the fixed shaft is inserted. The other end 2112 of the fixed shaft extends long in a direction of the driving shaft 212. One end 2121 of the driving shaft is rotatably coupled to the second frame 102.

The seating portion 1028 of the roller 210 may include a bearing 10282 such that one side 2121 of the driving shaft is rotatably seated. The other end 2122 of the driving shaft is disposed to face the other end 2112 of the fixed shaft and is rotatably coupled to the fixed shaft 211. The other end 2122 of the driving shaft may have a cylindrical shape surrounding the other end 2112 of the fixed shaft.

The rotating cylinder 214, which forms an outer surface of the roller 210 and has the teeth 2141 formed on an outer surface thereof and engaged with the support bars 1041, is coupled to the driving shaft 212 and rotates together with the driving shaft 212. The rotating cylinder 214 may be located on a circumference of the coil spring 213 and rotatably fastened with the driving shaft 212. One side of the rotating cylinder 214 may be coupled to the driving shaft 212, and the other side thereof may be formed in a shape surrounding a circumference of the other end 2122 of the driving shaft.

The coil spring 213 having one end coupled to the fixed shaft 211 and the other end coupled to the driving shaft 212 provides a rotational force to the roller 210. There is a form of the coil spring 213 providing elasticity in an axial direction, but a torsion spring that provides the elasticity to restore the original number of turns when the number of turns changes may be used as the coil spring 213 of the present disclosure.

Ends of the coil spring 213 may be bent so as to extend in a radial direction to be engaged with the fixed shaft 211 and a rotation axis, and the fixed shaft 211 and the driving shaft 212 may include coupling grooves into which the ends of the coil spring 213 are fastened. The coupling grooves may extend in a direction transverse to the rotation axis corresponding to the extension direction of the ends of the coil spring 213.

For the order of coupling, one side of the coil spring 213 is fixed to the fixed shaft 211 as shown in (a) in FIG. 19 . In order to insert the coil spring 213 into the fixed shaft 211 in a direction of the rotation axis, a first coupling groove 2113 of the fixed shaft 211 may extend to the other end of the fixed shaft 211. After inserting one side of the coil spring 213 into the first coupling groove 2113 of the fixed shaft 211, the rotating cylinder 214 is coupled to be located at an outer circumference of the coil spring 213 as shown in (b) in FIG. 19 .

Next, as shown in (c) in FIG. 19 , the driving shaft 212 is inserted in the direction of the rotation axis such that the other end 2132 of the coil spring and a second coupling groove 2123 of the driving shaft 212 are coupled to each other. Like the first coupling groove 2113, the second coupling groove 2123 may also extend to the other end 2122 of the driving shaft such that the coil spring 213 and the driving shaft 212 may be coupled to each other in the direction of the rotation axis. The other end 2132 of the coil spring is inserted into the second coupling groove 2123, and the driving shaft 212 is coupled to the rotating cylinder 214 so as to rotate together with the rotating cylinder 214.

FIG. 20 is a view showing a cross-section based on rotation of the roller 210, and shows a state in which the fixed shaft 211 is omitted. When the driving shaft 212 rotates relative to the fixed shaft 211, the number of turns of the torsion spring changes, and the torsion spring provides the elasticity to restore the original number of turns. In (a) in FIG. 20 , in the first state, one end 2131 and the other end 2132 of the coil spring 213 may extend in the radial direction and may have 90 ° therebetween (may not be limited to 90° and may have a different angle).

When the state of the mobile terminal 100 is switched, the roller 210 rotates. At this time, only the driving shaft 212 and the rotating cylinder 214 rotate, and the fixed shaft 211 does not rotate. Because the number of turns of the coil spring 213 changes, the angle between the bent one end 2131 and the other end of the coil spring 213 changes as shown in (b) in FIG. 20 .

When the state of the mobile terminal 100 is switched from the first state to the second state, the driving unit 200 moves the second frame 102 in the first direction, the variable portion of the display unit 151 moves, and the second region moves to the front of the mobile terminal 100. The support bars 1041 of the rolling hinge 104 located on the rear surface of the display unit 151 rotates the rotating cylinder 214 of the roller 210 by being engaged with the teeth 2141 of the roller 210.

The driving shaft 212 coupled to the rotating cylinder 214 rotates together, and the number of turns of the coil spring 213 changes. The coil spring 213 whose number of turns has changed has the elasticity to restore the original number of turns, and provides a force for the roller 210 to rotate in an opposite direction.

However, because the motor of the driving unit 200 restricts the movement of the second frame 102, the roller 210 is not able to rotate in the opposite direction. However, a pulling force may be provided to the display unit 151 such that the third region located at the front of the display unit 151 maintains a maximum flat state.

Conversely, when the state is switched from the second state to the first state, the driving unit 200 moves the second frame 102 in the second direction. When the second frame 102 moves in the first direction, the third region of the display unit 151 moves to the front and thus the slide frame 103 naturally moves in the first direction. However, when the second frame 102 conversely moves in the second direction, the force of the driving unit 200 is not directly transmitted to the slide frame 103, so that the movement of the slide frame 103 in the second direction may be slower than the movement of the second frame 102 in the second direction.

The coil spring 213 of the roller 210 provides a force for the third region of the display unit 151 to move to the rear of the mobile terminal 100 when the state is switched from the second state to the first state. More specifically, when the second frame 102 moves in the second direction, as the force of the driving unit 200 fixing the second frame 102 is removed, the coil spring 213 rotates the driving shaft 212 and the rotating cylinder 214 in the opposite direction so as to move the third region of the display unit 151 in a rearward direction corresponding to a moving speed of the second frame 102.

Thus, because of the roller 210 including the coil spring 213, the movement of the slide frame 103 may be synchronized with the movement of the second frame 102, and the display unit 151 may maintain the flat state.

FIG. 21 is a view showing arrangement of the rollers 210 coupled to the second frame 102 of the present disclosure. A region where the driving unit 200 is disposed may be disposed above the roller 210, and the roller 210 may include a plurality of rollers spaced apart from each other in the third direction.

As described above, the mobile terminal 100 of the present disclosure may adjust the size of the screen as needed, so that both portability and usability may be obtained.

In addition, in the mobile terminal 100 of the present disclosure, because stress is not concentrated at a specific point of the display unit 151, damage to the display unit 151 may be reduced.

In addition, the display unit 151 may be prevented from lifting when the second frame 102 moves, so that the display unit 151 in the flat state may be maintained.

In addition, when the state is switched from the second state to the first state, the roller 210 itself may provide a force to restore the first state to the display unit, so that the display unit may move in synchronization with the movement of the second frame 102.

The above-described embodiments are to be construed in all aspects as illustrative and not restrictive. The scope of the disclosure should be determined by the appended claims and their legal equivalents, not by the above description, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. 

What is claimed is:
 1. A mobile terminal capable of switching a state thereof from a first state to a second state extended in a first direction, the mobile terminal comprising: a first frame; a second frame capable of sliding in a first direction or in a second direction opposite to the first direction relative to the first frame; a roller coupled to an end in the first direction of the second frame; a flexible display unit including a fixed portion coupled to the first frame and a variable portion extending in a rearward direction from the fixed portion while surrounding the roller and having an area located at the front variable based on the sliding movement of the second frame; and a rolling hinge located on a rear surface of the variable portion and changing based on a shape of the variable portion, wherein the roller includes teeth formed on an outer surface thereof, wherein the rolling hinge includes irregularities corresponding to the teeth.
 2. The mobile terminal of claim 1, wherein the rolling hinge includes a plurality of support bars extending in a third direction perpendicular to the first direction and arranged adjacent to each other in the first direction, wherein the teeth of the roller include each protrusion inserted between adjacent two of the plurality of support bars.
 3. The mobile terminal of claim 1, wherein the roller includes: a fixed shaft fixed to the second frame; a driving shaft rotating relative to the fixed shaft; a coil spring having one side coupled to the fixed shaft and the other side coupled to the driving shaft; and a rotating cylinder rotating together with the driving shaft and having the teeth formed thereon.
 4. The mobile terminal of claim 3, wherein the rotating cylinder and the driving shaft rotate when the second frame moves and change the number of turns of the coil spring, wherein the coil spring provides elasticity to restore the reference number of turns to the driving shaft and the rotating cylinder.
 5. The mobile terminal of claim 4, wherein the elasticity of the coil spring is provided when restoring the first state from the second state.
 6. The mobile terminal of claim 3, wherein the second frame includes a roller seating portion for accommodating the roller therein at the end in the first direction thereof, wherein the roller seating portion includes: a fixing hole for receiving a screw fastened through one end of the fixed shaft; and a bearing for one end of the driving shaft to be rotatably seated.
 7. The mobile terminal of claim 3, wherein at least a portion of the driving shaft rotatably overlaps the fixed shaft inside of the coil spring.
 8. The mobile terminal of claim 3, wherein the fixed shaft includes a first coupling groove for receiving one end of the coil spring, wherein the driving shaft includes a second coupling groove for receiving the other end of the coil spring.
 9. The mobile terminal of claim 8, wherein both of the ends of the coil spring are bent in a radial direction of the coil, wherein the first coupling groove and the second coupling groove extend through a center of rotation of the driving shaft.
 10. The mobile terminal of claim 9, wherein the first coupling groove and the second coupling groove respectively extend to the other end of the fixed shaft and the other end of the driving shaft.
 11. The mobile terminal of claim 1, wherein the roller includes a plurality of rollers spaced apart from each other in a third direction perpendicular to the first direction. 